Step into Amazon.com's gleaming new headquarters in South Lake Union and you may wonder if the place is still under construction.

The industrial chic design goes way beyond the old Amazon desks that Jeff Bezos cobbled together in the early days out of cheap doors and raw lumber to emphasize the company's thrifty, scrappy culture.

Now, in the heart of Amazon, you'll find exposed ducts, bare concrete walls and dangling work lights that serve as light fixtures. It feels modern, hip and frugal — almost like a startup renting cheap space in a converted industrial building.

The underlying message is that Amazon is still moving fast. It's too busy building the future to worry much about embellishing rented space it may outgrow tomorrow.

This is more than surface décor. It reflects the mindset of a place that's focused and ready to move quickly when it sees the next big opportunity.

That's just what you want in a tech company. But Amazon's restless ambition — combined with its extraordinary secrecy, especially about future plans — has left Seattle in a kind of limbo, grateful for the company's growing presence, but wondering how long it would last.

Amazon reinforced that sense of uncertainty last year. It abruptly closed a big distribution center in Texas — where founder Bezos spent childhood summers at his grandfather's ranch — after the state tried to collect sales taxes from the online retail giant.

Meanwhile, Amazon steadfastly refuses to share details about its presence or plans for the Seattle area. This is in contrast to other big companies that tout their contributions to the region and the economy.

Amazon may be trying to avoid tipping off competitors, but it conceals the company's stature and leaves the impression that it's aloof and too inward to engage with its real-world community.

Until last week, that is, when this newspaper broke the news that Amazon has agreed to buy a large portion of precious downtown Seattle real estate and build at least three high-rise buildings.

This is remarkable for several reasons beyond the bold confidence it reveals.

The buildings would provide Amazon with 3 million square feet of additional space, nearly doubling the size of its sprawling headquarters campus built over the past four years.

They're comparable in scale to the campus redevelopment that Microsoft began in 2005. It spent more than $1 billion adding 3.1 million square feet in Redmond — including the absorption of a Safeco building — to accommodate up to 15,000 new employees.

Amazon's also unique among America's largest tech companies in building a headquarters downtown, instead of the suburban campuses Microsoft, Apple, Oracle, Google and IBM have developed.

It's also refreshing to have Amazon commit to a major development without first using the promise of jobs and growth to extract public subsidies. Apparently, Amazon's business plan is strong enough that it doesn't need Seattle and King County to provide hundreds of millions of dollars worth of revenue to proceed. (Although I may be speaking too soon: Amazon has yet to discuss the project, which its consultant submitted to the city last week.)

Most amazing of all, though, is the glimpse of what looks like a newfound sense of commitment and permanence.

Amazon tends to share about as much information as an introverted teenager, but it's turning 18 this year and finally putting down roots.

Information in this article, originally published Feb. 19, 2012, was corrected Feb. 20, 2012. A previous version of this story incorrectly said Amazon.com abandoned a partly built distribution center in South Carolina in a dispute with the state over sales taxes. In fact, Amazon completed the center and says it is now in operation.